Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/common/position_confidence.hpp

@@ -0,0 +1,32 @@
+#ifndef POSITION_CONFIDENCE_HPP_FNHKVJZL
+#define POSITION_CONFIDENCE_HPP_FNHKVJZL
+
+#include <vanetza/units/angle.hpp>
+#include <vanetza/units/length.hpp>
+#include <cmath>
+#include <limits>
+
+namespace vanetza
+{
+
+struct PositionConfidence
+{
+    PositionConfidence() :
+        semi_major(units::Length::from_value(std::numeric_limits<units::Length::value_type>::infinity())),
+        semi_minor(units::Length::from_value(std::numeric_limits<units::Length::value_type>::infinity()))
+    {}
+
+    operator bool() const
+    {
+        return !std::isinf(semi_major.value()) && semi_minor.value() <= semi_major.value() && semi_minor.value() >= 0.0;
+    }
+
+    units::Length semi_major;
+    units::Length semi_minor;
+    units::TrueNorth orientation;
+};
+
+} // namespace vanetza
+
+#endif /* POSITION_CONFIDENCE_HPP_FNHKVJZL */
+